Extraction process utilizing modified alkyl hydrazine solvent



Nov. 24, 1959 HARSHMAN 2,914,472

EXTRACTIBN PROCESS UTILIZING MODIFIED ALKYL HYDRAZINE SOLVENT Filed Nov. 12, 1958 INVENTOR.

' Richard C. Harshmon BY Bernard H. Nicolaisen WW MCM ATTORNEYS United States Patent EXTRACTION PROCESS UTILIZING Momrmn ALKYL HYDRAZINE SOLVENT Richard .C. I-Iarshman and Bernard M. Nicolaisen, Kenmore, N .Y., assignors to Olin Mathieson Chemical Corporation, a corporation of Virginia Application Novemberl-Z, 1958,'Serial No. 773,309 Claims. (Cl. 208-330) Thisinvention concerns a process for the extraction of normally liquid hydrocarbon mixtures with water, aqueous hydrazine or hydrazine and lower alkylhydrazines.

It has been found that, while hydrazine and its alkylsubstituted derivatives are generally miscible with one another, the various classes ofhydrocarbon compounds are generally immiscible with hydrazine and are miscible in varying degrees with alkylhydrazines. For example, 1,1-dimethylhydrazine shows greater solvent powers for aromatic hydrocarbons than for cycloparaflins, greater solvent powers for cycloparaffins than for branched chain aliphatic hydrocarbons and greater solvent powers for branched chain aliphatic hydrocarbons than for straight chain aliphatic hydrocarbons.

It has also been found that, when a hydrocarbon mixture containing componentsof the aforementioned various structural classes is admixed with a suitable alkylhydrazine, i.e,, one with which a particular structural class of hydrocarbon is miscible, and the resulting alkylhydrazine solution is admixed with water, aqueous hydrazine or hydrazine, preferably anhydrous hydrazine, a two-phase system results. The heavier, lower phase contains substantially all of the water, hydrazine and alkylhydrazine present and is enriched with respect to the hydrocarbon more miscible in the alkyl hydrazine. The lighter, upper phase is enriched with respect to hydrocarbons less miscible with the alkyl hydrazine.

"Thus, certain alkylhydrazines and water and/ or hydrazinernixtures are selective solvents for the various structural classes of hydrocarbons. With mixtures of hydrazine and an alkylhydrazine particular hydrocarbons can be, extracted from a more complex mixture of hydrocarbons and can be obtained in a purer form. Alternatively, mixtures of hydrazine, aqueous hydrazine or water with an alkylhydrazine can be used, for example, to remove from normally liquid hydrocarbon fuel mixtures those members whose presence lowers the octane number, o r'those members whose presence lowers the cetane number of the particular fuel.

These extractions can be made at any temperature between the freezing point of water, aqueous hydrazine or hydrazine and the temperature at which two liquid phases no longer form, even under pressure, or at which orient the components decomposes. Within this range, the phase containing the water and/or hydrazine, the alkylhydrazine and the hydrocarbons miscible therewith can be separated by suitable combinations of distillation and decantatiqn operations. The extraction can be done continuously in a counter-current extraction column wherein the hydrocarbons and the alkylhydrazine are admitted at the bottom of the column and hydrazine or water at the top. The extraction can also be performed batehwise using alkyl-hydrazines and hydrazine and/or water previously mixed.

The alkylhydrazine employed will be determined by the particular hydrocarbons present. For instance,where cyclic hydrocarbons are to be extracted, the use of 1,1-

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dialkylhydrazines is preferred. The mono-alkylhydrazines such as mono-methylhydrazine, mono-ethylhydrazine, mono-propylhydrazine and hexylhydrazine, are less soluble in the hydrocarbons and the triand tetra-alkylhydrazines, on the other hand, are less soluble in hydrazine and water. The 1,2-dialkylhydrazines are somewhat poorer solvents for hydrocarbons than the 1,1-dialkylhydrazines. This may be due to the symmetrical distribution of the alkyl groups in the 1,2-dialkylhydra-' zines, since the solvent power of these compounds for hydrocarbons appears to depend on the dialkyl portion of the molecule and the solubility in hydrazine and water appears to depend on the freedom of the unsubstituted portion to form hydrogen bonds. Among the 1,1-dialky1- hydrazines found to be especially useful are, for example, 1,l-dimethyl-, 1-methyl-, 1-ethyl-, and 1,1-diethylhydrazine.

The following examples illustrate the extraction method of this invention.

A charge of 98.4 grams of the above mixture is placed in a flask. It is cooled to 5 C. and grams of unsymmetrical dimethylhydrazine (1,1-dimethylhydrazine) is added With stirring. The temperature rises slightly, but is maintained below 20 C. throughout the experiment. After thorough mixing of the solution, 45 grams of anhydrous hydrazine are stirred into the latter. stirring is stopped, the hydrazine phase (lower) sepae rates and is removed by means of a separating funnel. The hydrocarbon phase (upper), containing the immiscible hydrocarbonand some unsymmetrical dimethylhydrazine, is again extracted with 45 grams of anhydrous hydrazine. After stirring, the'mixture separates into an upper hydrocarbon layer (phase A) containing the hydrazine-immiscible hydrocarbons and a hydrazine phase. The hydrazine phases drawn from the two extractions are then added together and the unsymmetrical dimethylhydrazine in the combined phases is distilled off. Then, after decanting the. immiscible hydrazine, the refractive index of the remaining mixture (phase B) containing the extracted cyclic-enriched hydrocarbon product is measured and compared with the refractive index of the original hydrocarbon mixture before extraction and with the refractive index of the upper hydrocarbon layer (phase A from which the cyclic hydrocarbons had been extracted. The refractive indices of the various mixtures are listed:

Although these results are accomplished with only a simple extraction, which is, of course, much less efficient than a continuous extraction column, it can be seen from the higher refractive index of the recovered hydrocarbon extract that the latter is enriched in its content of cyclics;

When the Example 11 A diesel fuel stock having a cetane number of 42 is extracted in the laboratory using a batch process to simulate a simple continuous extraction. A liter of the fuel stock is mixed with an equal volume of unsymmetrical dimethylhydrazine. To this solution is added with vigorous stirring a volume of anhydrous hydrazine equal to one-fourth the volume of the mixture. The mixture is allowed to stand and the heavier phase,-containing hydrazine, unsymmetrical dimethylhydrazine and extracted hydrocarbon is drawn oif. The extraction with hydrazine is repeated with a volume thereof equal to one-fourth the volume of the lighter, immiscible hydrocarbon phase and, after the second hydrazine phase is drawn off, the remaining hydrocarbon layer is treated with a second portion of unsymmetrical dimethylhydrazine. Extractions with hydrazine, using successive portions equal to one-fourth the volume of the hydrocarbon phase are then performed until no further change in volume of the hydrocarbon phase occurs. This treatment is found to increase appreciably the cetane number of the fuel stock,

indicating a selective removal of cyclic compounds.

Example III A liter of petroleum solvent fraction, having a Kauri- Butanol value (ASTMD-l135-54T) of 42, is mixed with half its volume of unsymmetrical dimethylhydrazine and this solution is extracted in a small, laboratory, countercurrent column with anhydrous hydrazine (B.P. 113.5 C.). The hydrazine phase is separated and distilled, removing unsymmetrical dimethylhydrazine (B.P. 63.l C.) overhead. After cooling, the hydrazine and extracted hydrocarbon in the bottoms are separated by decantation. This hydrocarbon product has a Kauri-Butanol value of 52, indicating a product appreciably higher in cyclic content than the feed stock.

Example IV 100 grams of the hydrocarbon mixture used in Example I is dissolved in an equal Weight of unsymmetrical dimethylhydrazine and the solution is extracted with two equal portions of anhydrous hydrazine. The hydrazine phase is separated, distilled and decanted as described in Example III and the hydrocarbon product is again treated with unsymmetrical dirnethylhydrazine and hydrazine as before. The final hydrocarbon product from this extraction shows, by infra-red analysis, an increase in cyclo-parafiin content of 25 percent.

Example V A mixture comprising 500 grams of benzene and 500 grams of petroleum ether is mixed with 500 grams of unsymmetrical diethylhydrazine. This is extracted in a small laboratory counter-current extraction tower with 1000 grams of 64% hydrazine solution. The mixture of hydrocarbons and diethylhydrazine is fed to the bottom of the tower and the hydrazine solution to the top of the tower. The hydrocarbon mixture removed from the top of the tower contains 70% by weight of aliphatic hydrocarbons.

Example VI A hydrocarbon fraction having a boiling range of 109-117" C. and containing 36% cyclo-paraflins as indicated by infra-red analysis is mixed with an equal weight of unsymmetrical dimethylhydrazine. A 100 gram portion of this solution is extracted with two separate gram portions of water. The separated hydrocarbon fraction is mixed with 50 grams of unsymmetrical dimethylhydrazine and extracted with two 10 gram portions of water. The aqueous phases from these extractions are combined and the dimethylhydrazine removed by distillation. The separated residual hydrocarbon showed a 14% increase in cyclo-paraflin content,

The single figure is a flow diagram further exemplifying this invention.

The mixed hydrocarbon feed is introduced into the extractor column 1 by means of line 3 and the alkylhydrazine is introduced through line 7. The extractor column can also advantageously have several alkylhydrazine feeds entering into its side, preferably no higher than two-thirds its height above the bottom of the column. Hydrazine and/or water is admitted through line 8. The raflinate is removed via overhead line 2, while the product-carrying solution, comprising hydrazine and/or water, alkylhydrazine and hydrocarbon mixture enriched in cyclics is led to the distillation tower 5 by means of line 4. The alkylhydrazine is withdrawn overhead through condenser 6 and is returned to 1 by means of line 7. Reboiler 9 in communication with column 5 taps the immiscible water and/ or hydrazine-cyclic hydrocarbon mixture. The latter proceeds to decanterll by means of line 10 where the lighter hydrocarbon layer is withdrawn through line 12. The hydrazine and/or water is returned to extractor 1 by means of line 8.

Replenishment of any hydrazines can be accomplished at any suitable location. For example, alkylhydrazine can be replenished with thefeed through line 3, while hydrazine or water may be replenished through line 8.

It should be noted that, in order for the decanter 11 to function, it must be fed a two-phase mixture, i.e., hy-, drocarbon and hydrazine and/or water. This requires that the alkylhydrazine boil at a lower temperature than is also suitable with hydrazine or hydrazine hydrate and hydrocarbons of suitably high boiling point.

What is claimed is:

1. A process for the extraction of a class of hydrocarbon from hydrocarbon mixtures containing at least two classes selected from the group of aromatic, cyclm paraffinic, branched chain aliphatic and straight chain aliphatic hydrocarbons comprising mixing at least one alkylhydrazine and a substanceselected from the group consisting of hydrazine, water and mixtures thereof with the said hydrocarbon mixture to produce atwo-phase system, a lower phase being enriched in comparison with the starting hydrocarbon mixture with the classes of hydrocarbons having a greater solubility in said alkylhydrazinc and an upper phase of said system being enriched in comparison with the starting hydrocarbon mixtures with the classes of hydrocarbons having a lesser solubility in said alkylhydrazine, separating the two phases, and recovering the hydrocarbons from ,the separated phases.

2. A process for the extraction of a class of hydrocarbon from hydrocarbon mixtures containing at least two classes selected from the group of aromatic, cycloparaffinic and branched chain aliphatic hydrocarbons comprising mixing at least one alkylhydrazine, said alkylhydrabine having solvent powers for the said classes in the order recited, said powers being greatest for the first recited class, and a substance selected from the group water, hydrazine and mixtures thereof w th the starting hydrocarbon mixture to produce a two-phase system, a lower phase being enriched in comparison with they start ing hydrocarbon mixture with the classes of hydrocarbons having a greater solubility in said alkylhydrazine and an upper phase of said system being enriched in comparison with the starting hydrocarbon mixture with the classes of hydrocarbons having a lesser solubilityin said alkylhydrazine, separating the two phases, and'recovering the hydrocarbons from the separated phases.

3. A process for the extraction of cyclic hydrocarbons from mixtures of cyclic and acyclic hydrocarbons comprising mixing at least one alkylhydrazine and a member of the group water, hydrazine and mixtures thereof with the said hydrocarbon mixture to produce a two-phase system, a lowerphase of said system being enriched in cyclic hydrocarbons in comparison with the starting hydrocarbon mixture and an upper phase of said system being enriched in acyclic hydrocarbons in com- 5 parison with the starting hydrocarbon mixture, separating the two phases, distilling the first phase to remove the alkylhydrazine overhead, and separating the cyclic hydrocarbons from the said first phase.

4. The process of claim 1 in which the alkylhydra- 10 zine is a 1,1-dialkylhydrazine.

5. The process of claim 1 in which the alkylhydrazine is 1,1-diamethylhydrazine and the hydrazine is anhydrous.

References Cited in the file of this patent UNITED STATES PATENTS Mayland et a1 Oct. 11, 1949 OTHER REFERENCES Strunk: Chemical Engineering Progress, vol. 54, No. 7, July 1958, pp. 45-48. 

1. A PROCESS FOR THE EXTRACTION OF A CLASS OF HYDROCARBON FROM HYDROCARBON MIXTURES CONTAINING AT LEAST TWO CLASSES SELECTED FROM THE GROUP OF AROMATIC, CYCLOPARAFFINIC, BRANCHED CHAIN ALIPHATIC AND STRAIGHT CHAIN ALIPHATIC HYDROCARBONS COMPRISING MIXING AT LEAST ONE ALKYLHYDRAZINE AND A SUBSTANCE SELECTED FROM THE GROUP CONSISTING OF HYDRAZINE, WATER AND MIXTURES THEREOF WITH THE SAID HYDROCARBON MIXTURE TO PRODUCE A TWO-PHASE SYSTEM, A LOWER PHASE BEING ENRICHED IN COMPARISON WITH 